It is known, e.g. from Austrian Pat. No. 320,362, to establish a positive connection between a pipe extremity and a resinous coupling sleeve overlapping same by forming that pipe extremity with a peripheral groove which is bounded by a peripheral rib on the side of the free end of that extremity, the sleeve having an inner peripheral bead engaging in the complementarily shaped pipe groove. More than one groove and rib can be provided on the same pipe extremity, e.g. as suggested in Austrian Pat. No. 329,333, with the coupling sleeve forming a corresponding number of peripheral beads respectively engaging in these grooves while overlapping the associated ribs. The coupling sleeve can be produced by coiling, casting or compression-molding.
Even with the use of hardened thermosetting materials such as epoxy resins reinforced by filaments in the form of rovings or whiskers of quartz glass, for example, a coupling sleeve of this description is susceptible to cracking under strong tensile and/or torsional stresses. The cracks tend to develop on the inner surface of a peripheral bead and to progress outwardly at an angle to the radial direction, as established by tests. Thus, the mechanical strength of the body of the sleeve can be utilized only in part.